The present invention relates to a refrigerating air-conditioning apparatus using a non-azeotropic mixed refrigerant, particularly to one that is capable of changing the composition of a refrigerant circulating through a refrigeration cycle such as to exhibit load-matching performance at all times of its operation.
FIG. 15 shows the layout of a conventional refrigerating air-conditioning apparatus using a non-azeotropic mixed refrigerant as proposed in Examined Japanese Patent Publication No. Hei 6-12201. In the drawing, numeral 1 refers to a compressor, 32 a condenser, 33 and 34 capillaries and 35 an evaporator; these components are connected by pipes sequentially to form a refrigeration cycle using a non-azeotropic mixed refrigerant consisting of a high-boiling point fraction and a low-boiling point fraction.
Shown by 11 is a refrigerant rectifying column, the bottom of which is connected to a loop including a heater 41 and a lower refrigerant container 42 whereas the top of the column is connected to a loop including a cooler 13 and an upper refrigerant container 14. The upper refrigerant container 14 is connected between the condenser 32 and the evaporator 35 via a solenoid valve 43 and so is the lower refrigerant container 42 via a solenoid valve 44. Provided upstream of the evaporator 35 are a capillary 45 and a solenoid valve 46, via which the evaporator is connected to the upper refrigerant container 14; the evaporator 35 is also connected to the lower refrigerant container 42 via the capillary 45 and a solenoid valve 47. The heater 41 is an electric heater and the cooler 13 is a water-cooled heat exchanger.
Being constructed in the way just described above, the prior art refrigerating air-conditioning apparatus using a non-azeotropic mixed refrigerant is operated in the following manner. The vapor of a non-azeotropic mixed refrigerant compressed to a higher temperature and pressure in the compressor 1 condenses in the condenser 32 and flows into the capillary 33. During normal operation, solenoid valves 43, 44, 46 and 47 are closed so that the refrigerant passes through the capillary 34 to turn into a low-temperature and pressure refrigerant consisting of a vapor and a liquid phase, which then flows into the evaporator 35 and the resulting vapor returns to the compressor 1.
In order to increase the high-boiling point fraction of the refrigerant circulating through the refrigeration cycle, the following procedure may be taken. Solenoid valves 43 and 46 are closed and solenoid valves 44 and 47 are opened so that a portion of the refrigerant emerging from the capillary 33 is diverted to solenoid 44, thence flowing into the lower refrigerant container 42. A portion of the refrigerant entering the lower refrigerant container 42 passes through solenoid 47 to flow into the capillary 45, where it merges with the refrigerant flowing through the main circuit on the side upstream of the evaporator 35. The remainder of the refrigerant entering the lower refrigerant container 42 is heated in the heater 41 and the resulting vapor ascends through the refrigerant rectifying column 11. At the same time, the liquid refrigerant stored in the upper refrigerant container 14 descends through the refrigerant rectifying column 11 and contacts the ascending refrigerant vapor to perform a so-called "rectifying action" by the resulting vapor-liquid contact. As it ascends through the rectifying column 11, the refrigerant vapor becomes enriched with the low-boiling point fraction. It is then liquefied in the cooler 13 and collects in the upper refrigerant container 14; thus, only the refrigerant rich in the low-boiling point fraction is stored in the upper refrigerant container 14. In other words, the remainder of the refrigerant which flows through the refrigeration cycle is enriched with the high-boiling point fraction.
In order to increase the low-boiling point fraction of the refrigerant circulating through the refrigeration cycle, the following procedure may be taken. Solenoid valves 43 and 46 are opened and solenoid valves 44 and 47 are closed so that a portion of the refrigerant emerging from the capillary 33 is diverted to solenoid valve 43, thence flowing into the upper refrigerant container 14. A portion of the refrigerant entering the upper refrigerant container 14 passes through the capillary 45 and emerges with the main circuit stream, and the remainder of the refrigerant enters the refrigerant rectifying column 11, through which it descends. At the same time, a portion of the liquid refrigerant in the lower refrigerant container 42 is heated in the heater 41 and the resulting vapor ascends through the refrigerant rectifying column 11 to contact the descending liquid refrigerant, thereby achieving a so-called "rectifying action" through the resulting vapor-liquid contact. The descending liquid refrigerant becomes gradually enriched with the high-boiling point fraction and collects in the lower refrigerant container 42; thus, only the refrigerant rich in the high-boiling point fraction is stored in the lower refrigerant container 42. In other words, the remainder of the refrigerant which flows through the refrigeration cycle is enriched with the low-boiling point fraction.
Another example of the prior art apparatus may be found in Examined Japanese Patent Publication No. Hei 2-47668.
As described above, the conventional refrigerating air-conditioning apparatus which uses a non-azeotropic mixed refrigerant utilizes a refrigerant rectifying column in order to increase both the high-boiling and low-boiling point fractions of the refrigerant circulating through the refrigeration cycle; therefore, the overall circuit configuration is complicated and energy is required at all times of the cooling and heating operations. In particular, the use of an electric heater requires extra power input when the refrigerant composition is changed and this reduces the energy efficiency of the refrigerating air-conditioning apparatus.
In addition, the performance of the apparatus cannot be controlled over a practically broad dynamic range by merely changing the composition of the refrigerant; in order to deal with this difficulty, the additional control of the performance by changing the rotational speed of the compressor with an inverter may be invoked. This approach is capable of increasing the dynamic range of performance control but, on the other hand, due to the loss in the inverter or motor, the change in the rotational speed of the compressor eventually lowers the efficiency of the refrigerating air-conditioning apparatus.